Thanks for your advice @bcworkz
I asked the Avada support channel and the fix wasn’t available out of the box.
However, I’ve found 2 really good plugins that helps the issue.
https://www.ads-software.com/plugins/remove-cpt-base/ – this removed the Avada_portfolio part of the case studies URL.
https://permalinkmanager.pro – this allowed me to add /case-studies/ and /insights/ at the beginning of both post types. Here’s what they look like now:
https://clickzilla.co.uk/case-studies/seo/bet90/
https://clickzilla.co.uk/insights/link-building/how-to-choose-digital-pr-agency/
This is exactly what I wanted, so it’s great. Also the Permalink Manager Pro plugin also allows you to change the category URLs, although I’ve not done that just yet.
The only thing left to work out is the breadcrumbs, as they are missing out Insights and Case Studies at the moment, I’m speaking to the support channel about this.
If I find a fix, I’ll comment in this thread. I don’t think it will be possible out of the box.
Thanks!